1. Field of Invention
The invention relates to a method for forming a silicon oxide layer, more particularly to a method for forming a silicon oxide layer in the production of polysilicon film transistors.
2. Related Art
Mechanical, electronic and semiconductor industries usually include the formation of a material layer with certain properties over its components. The layer is usually deposited at the atomic or molecular level, which has a structure that cannot be obtained by thermal equilibrium.
Conventionally, a film deposition process may be performed through a physical vapor deposition (PVD) or a chemical vapor deposition (CVD) according to the participation of a chemical reaction mechanism. The deposited layer may have a monocrystalline, polycrystalline or amorphous structure, depending upon the conditions of deposition. The characteristics of the deposited layer can be useful in various fields. For example, a buffer layer and a precursor layer are commonly used in the production of low-temperature polysilicon film transistors. The precursor layer is created by through forming an amorphous silicon layer on a substrate, and then raising the temperature of the amorphous silicon layer to its melting point by excimer laser annealing (ELA). As the amorphous silicon layer is subjected to the energy of the excimer laser wavelength, it starts melting and becomes a polysilicon structure. Before excimer laser annealing, the formation of a silicon oxide layer over the amorphous silicon layer is usually needed. Therefore, the substrate with the amorphous silicon layer thereon has to be transferred into a cleaner to form the silicon oxide layer over the amorphous layer by rinsing in an ozone aqueous solution.
A plasma-enhanced chemical vapor deposition (PECVD) has the advantages of being performed in lower temperature conditions with a high deposition rate and good step coverage. The current production process of low-temperature polysilicon performs the PECVD on the substrate to deposit a spacer layer and an amorphous layer. After the amorphous silicon layer is formed, the substrate is subject to oxidation, which easily causes contamination and increases the production time.